Several bugs have been found in the ISAKMP daemon which can lead to memory 
leaks and a remote denial of service condition. An attacker can craft 
malformed payloads that can cause the isakmpd(8) process to stop 
processing requests.

The problem is fixed in -current, 3.4-stable and 3.3-stable.

Patches are available at:

   ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.4/common/015_isakmpd2.patch
   ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.3/common/020_isakmpd2.patch